Goliath cranes such as unloaders which are installed in quays use grab buckets which grab and land loose bulk materials such as coal and sand from holds. The grab buckets are hoisted or hoisted down and opened or closed by a remote operation in an operator's cabin of a crane, but these operations can be performed only on grab buckets which are attached to cranes via wire ropes. The buckets, therefore, cannot be transported to another places. Steel materials, steel scrap, and the like can be hoisted or hoisted down by lifting magnets, but when they are stacked, only they near the surface can be attracted by the lifting magnets. The most efficient and general cargo work units are, therefore, units using containers (bags), but in the case of containers, loading and discharging take a along time, and this case is not efficient. Further, in the case of a container bottom plates of which are opened or closed and contents of which are discharged, there arise safety problems such that an worker who opens or closes the bottom plates cannot be seen by an operator in a crane, and the worker might be injured by dropping discharged contents. Therefore, some containers have been proposed. In using the containers, a preparing operation such that bottom plates are automatically opened when containers are hoisted down, landed, and again hoisted, is performed in advance, workers do not have to reach at the time of discharging contents.
One example of such containers is shown in FIG. 14. Reference numeral 1 designates a container made of a steel plate, reference numeral 11 designates an opening/closing type bottom plate, and reference numeral 12 designates a hinge for opening or closing the bottom plates 11. Reference numeral 13 designates a locking pin which is provided near a distal end of the bottom plate 11 to be opened or closed and which restricts opening of the bottom plates 11 by means of an open/close control mechanism, mentioned below, and reference numeral 14 is a side plate of the container 1. Reference numeral 3 designates a hoisting portion which is provided near the bottom plates 11 and used when the container 1 is hoisted by a crane, and reference numeral 18 designates a fork hole which is used for loading the container 1 using a forklift or the like. In this drawing, a roof portion of the container 1 is opened, but it is occasionally covered by a sheet or the like.
FIG. 15 is a perspective view illustrating a state that the container 1 is hoisted by using a hoisting frame 2 and the bottom plates 11 are opened. Reference numeral 21 designates an auxiliary wire rope which is used between the hoisting frame 2 and the hoisting portion 3 of the container 1, and reference numeral 431 designates a hook portion which locks the locking pin 13 with a main body of the container 1.
As to such kind of container, the hook portion 431 is locked and the bottom plates 11 are not opened, normally. When, however, contents are discharged, the preparing operation for releasing lock is performed in advance, and the container is hoisted and landed, so that the hook portion 431 is released and the bottom plates 11 are opened. Not shown in FIGS. 14 and 15, an open/close control mechanism is provided near the hook portion 431, namely, near the bottom plates 11.
As one conventional example of the open/close control mechanism, one embodiment of the bottom opening type container disclosed in Japanese Patent No. 332114 is explained with reference to the drawings. This container is of bottom opening type, and it is hung at four points on the bottom portion illustrated above in FIG. 15.
FIG. 16 is a front view illustrating the open/close control mechanism 4 of the conventional bottom opening type container. Parts which are common to those explained above are designated by the same reference numerals. Reference numeral 31 designates a hoisting plate which extends from four corners on the bottom portion of the container 1, reference numeral 32 designates a hoisting hole provided on outer end of the hoisting plate, reference numeral 34 designates an intermediate link which connects the hoisting plate 31 and an upper end of an open/close arm 43 which restrains the bottom plate 11, reference numeral 42 designates a rotary rod which is attached to the bottom portion of the side plate 14 in a vertical direction, reference numeral 432 designates a pressing portion which is provided to upper and lower two places of the side surface of the open/close arm 43 and locks an elevating block 422 in open and closed positions of the open/close arm 43, reference numeral 423 designates a spring retaining sleeve, reference numeral 49b designates a pressing-down spring which assists a empty weight of the elevating block 422 and presses it down.
In the open/close control mechanism 4, an operation lever 421 is turned so that the rotary rod 42 which is integral with the operation lever 421 is rotated, and the open/close arms 43 which lock the distal ends of the bottom plates 11 are controlled so as to be opened or closed according to positions, upper or lower, of the elevating block 422 into which the rotary rod 42 is inserted and which is engaged with the rotary rod 42 and elevates in an interlocking manner, and the open/close operation of the open/close arms 43 is performed by the hoisting plates 31 connected to them via the intermediate links 34.
The using method of the container 1 is explained below. Since the open/close control mechanism 4 is constituted symmetrically, only one side is explained with reference to the drawings. In order to secure the open/close control safely, it is desirable that the open/close control mechanism 4 is provided also to the other side in FIG. 15. For this reason, four sets of mechanisms corresponding to FIG. 17 are provided to one container 1.
FIG. 17 illustrates a basic state that the bottom plates 11 are closed the same as FIG. 16, and corresponds to the left half portion of FIG. 16. The operation lever 421 faces a left side with respect to the rotary rod 42. According to the engagement of a groove portion of the rotary rod 42 and the elevating block 422, mentioned below, the elevating block 422 is in an ascended position. The open/close arm 43 is biased by an open spring 49a to an open direction, but an upper pressing portion 432a of two pressing portions provided to an upper and a lower portions of the side surface of the open/close arm 43 presses the elevating block 422, so that the open/close arm 43 cannot be opened. If, therefore, the container 1 is hoisted and landed in this state, the bottom plates 11 are not opened.
In the landed state, as shown by an arrow of FIG. 17, the operation lever 421 is pulled to a front side so as to be rotated to a right side. The rotary rod 42 rotates and the elevating block 422 can be descended, but since the open/close arm 43 still presses the elevating block 422 due to the open spring 49a, the elevating block 422 cannot descend yet.
A wire rope is inserted into the hoisting hole 32 so that the container 1 is hoisted. The hoisting plate 31 is rotated by a fixed pin 47a, and the intermediate link 34 and the upper end of the open/close arm 43 are drawn via a link pin 48a. For this reason, the elevating block 422 is released from the open/close arm 43 so as to drop and is in a middle position on a stepped portion of the lower pressing portion 432b. This state is shown in FIG. 18.
When the container 1 reaches destination and the container 1 is once landed, the force for hoisting the hoisting plate 31 is weakened, the open/close arm 43 is opened by the function of the open spring 49a, and the elevating block 422 drops to the lower end, and the open/close arm 43 is pressed against the pressing portion 432b so as to be maintained in the opened state. This state is shown in FIG. 19. When the container 1 is hoisted in this state, the bottom plates 11 are opened due to the weight of the contents and the empty weight of the bottom plates 11 so that the contents are discharged.
That is to say, when the operation lever 421 is in the basic state where it is directed left, the bottom plate 11 is not opened, and only when the operation lever 421 is directed right so that the container 1 is landed and hoisted, the bottom plates 11 are opened. When the operation lever 421 is returned to the left, the container 1 is once landed, and the bottom plates of which are closed, and the container 1 is hoisted, the container 1 is returned to original state thereof. When the elevating block 422 does not drop securely due to its empty weight even if the rotary rod 42 rotates, it is desirable that the pressing-down spring 49b which biases the elevating block 422 downward, is suitably inserted. The spring retaining sleeve 423 receives the pressing-down force so as to transmit it to the elevating block 422.
FIG. 20 illustrates a section of a portion formed with the groove portion 424 of the rotary rod 42, and FIGS. 21A and 21B are perspective views in an A position and a B position of the groove portion 424 formed on the side surface of the rotary rod 42. A set pin, not shown, protrudes from the elevating block 422 towards the rotary rod 42 so as to be engaged with the groove portion 424. When the groove portion 424 is developed, it is a right-angled triangle where hypotenuse is lower side, and a groove of an up-and-down direction is provided on the left side, namely, the position A of FIG. 20, and the opposite side, namely, the position B of FIG. 20 is an apex, and thus a freedom of an up-and-down direction is not provided. The basic state that the bottom plates are closed, namely, a state that the operation lever 421 directs the left is the position B, and a state that the operation lever 421 is released, namely, directs the right is the position A. After the elevating block 422 drops along the groove in the up-and-down direction of the groove portion 424 in the position A, when the operation lever 421 is returned to the left, the elevating block 422 ascends along the hypotenuse of the groove portion 424, so as to return to the position B.
The above-mentioned bottom opening type container is constituted so that after the preparing operation is performed in advance, when the bottom opening type container is transported, hoisted down in a load discharge place so as to be landed, and hoisted again, the bottom plates are automatically opened. A worker does not have to be near the container when the contents are discharged. The problem of safety is solved, but the following problems remain and thus they are desirably further solved;
a) a number of parts is large and the constitution is complicated, and when mechanical resistance such as frictional force is large, the container is not opened, and thus the opening operation is not secure;
b) a check cannot be made externally whether the preparing operation for opening is performed or not; and
c) when the open/close control mechanism 4 is provided also to the other side of the container, in order to perform the preparing operation for opening, the worker should approach both the sides of the container.